I did the same thing a few years ago. I bought one of these adapters:

http://chucker54.stores.yahoo.net/mamastad.html

I also bought a used manual steering box and it was a simple swap.

If you wanted to buy a new manual steering box, I would consider checking out FirmFeel. A few years ago, I bought a quick ratio power steering unit from them and I really liked it. I would think their manual steering boxes are pretty good too.

http://www.firmfeel.com/manualst.htm